(i) Field of the Invention
The present invention relates to an optical disc recording velocity determining method for determining a recording velocity at which information can satisfactorily be recorded in optical discs such as a compact disc-recordable (CD-R) and a compact disc-rewritable (CD-RW).
The present invention relates to an optical disc writing laser power determining method for determining a writing laser power value at which information can satisfactorily be recorded in optical discs such as a compact disc-recordable (CD-R) and a compact disc-rewritable (CD-RW).
(ii) Description of Related Art
As a conventional recording method with respect to the optical discs such as a CD-R and a digital versatile disc-recordable (DVD-R), a high-velocity recording is performed at a multi-times linear velocity (e.g., double velocity, four-times velocity, . . . , and the like) higher than a standard linear velocity (one-time velocity).
By a change of a so-called strategy for adjusting a writing laser power, irradiation time, irradiation start timing, and the like in accordance with a recording velocity magnification, the recording has heretofore been performed with a negligible recording error in the respective recording velocities.
However, some types of the optical disc to be recorded do not meet the high-velocity recording. Therefore, when the recording is performed with respect to these optical discs at the high velocity, a recording error is generated at a high possibility. Moreover, even with the recording with respect to the optical disc which can meet the high-velocity recording, the recording error is sometimes generated depending upon compatibility of a recording apparatus with the optical disc. When such a recording error is generated, the data area cannot be reproduced correctly.
An optical power control (OPC: adjustment of an optimum write power of a laser beam) has been implemented which comprises: performing a test recording at a plurality of recording velocities in a predetermined area in the optical disc prior to a regular recording; and obtaining a writing laser power with which an optimum recording can be performed at the tested recording velocity. However, an available and preferable velocity range at which the recording can be performed well cannot be determined under the OPC. If the optimal recording velocity range can be determined with respect to a combination of the optical disc type to be recorded and the recording apparatus for performing the recording on the optical disc, the recording error is suppressed with the corresponding combination of the optical disc and the recording apparatus, and it is possible to perform the recording in a shorter time. However, an effective method for determining a range of the recording velocity at which the satisfactory recording can be realized has not been heretofore proposed.
As a method for controlling a write laser power to be optimum in accordance with a recording velocity magnification, the OPC method of implementing an optimum power control has been proposed which comprises: performing a test recording with a plurality of writing laser power values in a predetermined area in an optical disc prior to a regular recording; and obtaining a writing laser power value from a reproduction result of the test recording area.
In the conventional OPC, a writing laser power value/β value characteristic indicating a relation between the writing laser power value and the β value is obtained from a reproduced signal from a test record area, and is referred to, and the writing laser power value corresponding to a predetermined optimum β value is employed as an optimum writing laser power value. Additionally, the β value is a parameter relating to a reproduced signal level or amplitude, and is obtained by (a+b)/(a−b) in which character a denotes a peak level (with a sign of +) of an eight to fourteen modulation (EFM) signal waveform as a returned light receiving signal of an optical pickup, and b (with a sign of −) denotes a bottom level of the returned signal.
Additionally, in the conventional OPC, the writing laser power value corresponding to the predetermined optimum β value is determined. That is, the writing laser power value is determined considering only the β value. However, when a characteristic of the optical disc differs from a type to type, a quality level of a recording state is deteriorated during recording with the writing laser power value determined simply by considering only the β value. For example, a relation between the writing laser power value and the β value is usually substantially linear, but sometimes turns to a nonlinear relation shown in FIG. 49 because of distortion, dyestuff unevenness, and the like of the optical disc. As shown in FIG. 49, in the optical disc, the relation between the β value and the writing laser power value has a substantially linear characteristic excluding a part BT (the vicinity of a β value of 10, and the vicinity of a writing laser power value of 16 mW in the shown example). During the recording with respect to the optical disc having such a characteristic with the writing laser power value (e.g., 16 mW) corresponding to the β value significant point BT at which the β value significantly changes, a satisfactory recording state quality cannot sometimes be obtained.